|Type||Fortified rice wine|
|Country of origin||Korea|
|Region of origin|
|Related products||cheongju, soju|
Gwaha-ju (과하주; 過夏酒; lit. "summer-passing wine") is a traditional Korean fortified rice wine. The refined rice wine cheongju (also called yakju) is fortified by adding the distilled spirit soju to produce gwaha-ju. Popular varieties include gangha-ju (강하주) of Boseong and Yeonggwang in South Jeolla Province, sinseon-ju (신선주) of Namwon in North Jeolla Province, and yak-soju (약소주) of Suwon in Gyeonggi Province.
The word gwaha-ju (Korean: 과하주; Hanja: 過夏酒) consists of three syllables: gwa (Korean: 과; Hanja: 過) meaning "to pass" or "to last", ha (Korean: 하; Hanja: 夏) meaning "summer", and ju (Korean: 주; Hanja: 酒) meaning "alcoholic beverage". The name suggests that the rice wine retains its flavor after the hot and humid summer, due to the fortification (addition of soju).
Regional varieties of gwaha-ju are called by their own regional names such as gangha-ju (강하주; 薑荷酒), sinseon-ju (신선주; 神仙酒; lit. "(Taoist) Immortal's wine"), and yak-soju (약소주; 藥燒酒; lit. "yakju cum soju'").
Other names mentioned in old documents include gwaha-baekju (과하백주; 過夏白酒; lit. "pass-summer white wine") in Sanga Yorok, a mid-15th century cookbook, and ohyang-soju (오향소주; 五香燒酒; lit. "five flavour distilled liquor") in Imwon gyeongjeji, an 1827 encyclopedic compilation.
Gwaha-baekju was first mentioned in Sanga Yorok, a mid-15th century cookbook, but the rice wine was made without fortification. The earliest recorded recipe for fortified gangha-ju appears in Eumsik dimibang, a 1670 cookbook. Other Joseon books that mention the fortified rice wine include Jubangmun, Chisaeng yoram, Yeokjubangmun, Eumsikbo, Sallim gyeongje, Jeungbo sallim gyeongje, Gyuhap chongseo, and Imwon gyeongjeji.
Gwaha-ju was a devised product for hot and humid summers in the Korean Peninsula, during which regular cheongju (rice wine) was hard to brew and easily spoiled, and regular soju (distilled liquor) was too strong. The fortified rice wine was a luxurious prestige drink made in the wealthy households of yangban gentries in the early 15th century, but gradually spread and became popular among commonality.
Many legacy gwaha-ju recipes disappeared due to the harsh periods of Japanese forced occupation (1910–1945) and the Korean War (1950–1953). Today, only a few regional varieties such as gangha-ju (강하주; 薑荷酒) of Boseong and Yeonggwang in South Jeolla Province, sinseon-ju (신선주; 神仙酒) of Namwon in North Jeolla Province, and yak-soju (약소주; 藥燒酒) of Suwon in Gyeonggi Province, survive, with the recipes being transmitted within families.
A recipe for gwaha-ju in the 17th century cookbook Eumsik dimibang states: 
A bottle of boiled and cooled water is added to nuruk (fermentation starter) powder and set aside overnight, strained with additional sterile water. A mal (18 L, 4.0 imp gal, 4.8 US gal) of glutinous rice is steamed, cooled, and mixed with the nuruk-solution. After 3 days of primary fermentation, 20 bokja (9–10 L, 2.0–2.2 imp gal, 2.4–2.6 US gal) of soju (distilled liquor) is added to the rice wine. The fortified rice wine is consumed after 7 days of secondary fermentation.
A recipe for gwaha-ju in the 1809 encyclopaedia Gyuhap chongseo states: 
1–2 doe (1.8–3.6 L, 0.40–0.79 imp gal, 0.48–0.95 US gal) of white non-glutinous rice is cooked into beombeok (thick porridge), cooled, and mixed with nuruk powder. A mal (18 L, 4.0 imp gal, 4.8 US gal) of glutinous rice is steamed, cooled, and mixed with the nuruk mixture. After 7 days of primary fermentation, 20 bokja (9–10 L, 2.0–2.2 imp gal, 2.4–2.6 US gal) of soju (distilled liquor) is added to the rice wine.
Today, family recipes passed down through generations usually utilize various medicinal herbs as supplementary ingredients. A recipe in the 1827 document Imwon gyeongjeji states that ohyang-soju (five flavour distilled liquor) is made by: "brewing rice wine with cooked glutinous rice and nuruk (fermentation starter); adding powdered herbs such as sandalwood, costus, snowparsley, and clove, as well as whole walnuts and jujubes and soju (distilled liquor) after the primary fermentation; sealing hermetically for the secondary fermentation; opening the wine jar after 7 days and sealing again; and letting age for 29 days."
Boseong gangha-ju is the fortified rice wine brewed in Do Hwa-ja's house in Boseong County, South Jeolla Province. The family recipe uses jujubes, ginger, and gotgam (dried persimmon).
Namwon sinseon-ju is the fortified rice wine brewed in Gim Gil-im's house in Namwon, South Jeolla Province. The family recipe uses pine needles, mung beans, chestnuts, ginseng, dried poria, and bamboo leaves.
Suwon yak-soju is the fortified rice wine brewed in Gim Myeong-ja's house in Suwon, Gyeonggi Province. The family recipe uses longan, dried ginseng, steamed jujubes, ginger juice, and cinnamon.
Yeonggwang gangha-ju is the fortified rice wine brewed in Jo Hui-ja's house in Yeonggwang County, South Jeolla Province. The family recipe uses roasted goji berries, steamed jujubes, ganghwal, longan, and ginger juice.